A microphone preamplifier is a sound engineering device that prepares a microphone signal to be processed by other equipment. Microphone signals are normally too weak to be transmitted to units such as mixing consoles and recording devices. Preamplifiers increase a microphone signal to line-level (i.e. the level of signal strength required by such devices) by providing stable gain while preventing induced noise that would otherwise distort the signal.[1]
The microphone preamplifiers are colloquially called microphone preamp, mic preamp, preamp (not to be confused with a control amplifier in high-fidelity reproduction equipment), mic pre and pre.
The output voltage on a dynamic microphone may be very low, typically in the 0 to 100 microvolt range. A microphone preamplifier increases that level by up to 70 dB, to approximately 0 to 10 volts. This stronger signal is used to drive equalization circuitry within an audio mixer, to drive external audio effects, and to sum with other signals to create an audio mix for audio recording and for live sound.
A microphone is a transducer and, as such, is the source of much of the coloration of an audio mix. Most audio engineers would assert that a microphone preamplifier also affects the sound quality of an audio mix. A preamplifier might load the microphone with low impedance, forcing the microphone to work harder and so change its tone quality. A preamplifier might add coloration for adding a different characteristic than the audio mixer's built-in preamplifiers. Some microphones must be used in conjunction with a preamplifier to function properly (e.g.Condenser microphones)
Some preamplifiers exist as one part of a channel strip, which can include other kinds of audio recording devices such as compressors, equalization (EQ), noise gates, and enhancers.
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